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Pre-AP Chemistry 11 extensionAtomic Theory VIName:Date:Block:HybridizationMolecular Orbital TheoryHybridization VSEPR theory is useful in predicting the repulsion that occurs between bonding and/or non-bonding pairs of electrons and can be used to predict molecular shape. However, there are some limitations and over simplifications. Valence bond theory describes the location of bonding and non-bonding, lone electrons in quantum-mechanical orbitals, created by overlap of the standard s, p, d and f orbitals. Hybridization is a mathematical process in which these standard atomic orbitals are combined to form new atomic orbitals called hybrid orbitals. Example: CH4Each hydrogen has ______ valence electron existing in the ______ orbital. Carbon has ______ valence electrons, two existing in the ______ orbital and two existing in the ______ orbital. (The 1s electrons are not affected).The s and p orbitals combine to form four identical bonding orbitals, designated ________. Each of these can share their electron with one hydrogen atom. The region in space occupied by a pair of bonding or lone electrons, regions of high electron density, is a “domain”.***sp3d and sp3d2 are not being assessed on the AP Chemistry exam. Sigma (σ) and Pi (π)Bonding Sigma (σ) Bonding Occurs when two atomic orbitals combine to form a covalent bondExample: H2Pi (π)Bonding Occurs when two unhybridized p orbitals overlapA double bond consists of one sigma and one pi bond overlapExample: C2H4Draw the Lewis structure for ethene:sp and sp2 hybridizationDouble and triple bonds are commonly associated with carbon atoms and always consist of one sigma (σ) and one or two pi (π) bonds. Practice:Determine the shape and hybridization for the following. Determine the number of sigma and pi bonds in the molecule: CH2OHCNOF2SF6Molecular Orbital Theory MO theory enhances our ability to predict molecular structures.Accurately predicts:Bond energyBond lengthBond orderParamagnetism or diamagnetismMolecular orbitals are formed from atomic orbitals. Consistent with the Pauli exclusion principle, molecular orbitals hold a maximum of _______ electrons, each with opposite spin. Bonding orbital: The first orbital will have a lower potential energy and be more stable. Antibonding orbital:The second orbital will have a higher potential energy and be unstable. Specified with an asterisk. (σ* = sigma star)Molecular Orbital DiagramProvides information about bond order, bond length, bond energy, and magnetic behaviour. Bond order= # of bonding electrons-# of antibonding electrons2The calculated bond order is analogous to the number of bonds between atoms.Bond order of 0 = impossible bondBond order of 1 = single bondBond order of 2 = double bond.Bond order of 3 = triple bond.Quadruple bonds do not occur.Fractional bond orders are indicative of resonance = electrons are shared. Bond order is directly proportional to bond energy.Single bonds have the ________________ energy and are the ________________ bonds.Triple bonds have the ________________ energy and are the ________________ bonds.Bond order is inversely proportional to bond length.Single bonds are the ________________ bonds.Triple bonds are the ________________ bonds. Practice 1.Draw a molecular orbital diagram for the following molecules. What is its bond order? What does this indicate about the bonding and the stability of the molecule? Li2Be2MO diagrams for larger molecules do not include the core electrons. This is because the cores of such molecules contain equal numbers of bonding and antibonding electrons and so the effects of these electrons cancel out. MO diagram for a fluorine molecule: Paramagnetism = one or more electrons are unpaired.Diamagnetism = all electrons are paired.Draw the Lewis structure for NO:MO diagram for NO:NO-NO+Lewis diagram:Lewis diagram:MO diagram:MO diagram:Bond order:Bond order:Type of bond:Type of bond: ................
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